Journal of the Australian Ceramic Society最新文献

ZrO₂ is widely used. However, surface hydrophilicity is harmful to waterproof devices. In this work, epoxy-based polyhedral oligomeric silsesquioxane (POSS) was chemically bonded to ZrO₂ sheet surface for weather-resistant hydrophobicity and anti-adherence property. First, ZrO₂ sheet was modified with hydroxyls, followed by amino modification. Then, surface POSS modification was performed via ring-opening addition. Next, composition and micro-morphology of POSS-treated sheet were clarified. Ultimately, the dependence of water contact angle of POSS-modified sheet on POSS solution treating time was researched, and the highest contact angle of 132.6° was gained by 24-h treating. Acid corrosion, alkali corrosion, and ultraviolet radiation for 48 h were employed to verify good weather resistance with contact angles over 120°. POSS-modified sheet had good anti-adherence capacity. Cooperation of POSS and ZrO₂ was utilized to obtain low surface energy and high surface roughness. This work might help to obtain hydrophobic ceramics as catalyst supports for oil-phase reactions.

This study explored the effects of PtCo/C catalysts modified by microwave radiation as anode and cathode catalysts in proton exchange membrane (PEM) fuel cells. The PtCo/C catalyst was synthesized using sodium borohydride and formic acid-reducing agents by a chemical reduction method. The structural properties of PtCo/C and modified PtCo/C catalysts were analyzed by XRD analysis. The composition and distribution of these alloys in Vulcan XC-72R carbon were determined by SEM techniques. The electrochemical properties of the catalysts were evaluated by CV studies. The tafel slope b values for PtCo/C and modified PtCo/C catalysts were calculated as 84 mV/dec and 43 mV/dec when used as cathode catalysts, and 54 mV/dec and 41 mV/dec when used as anode catalysts, respectively. The power density values were calculated as 52 mW/cm² and 58 mW/cm² when PtCo/C and modified PtCo/C were used as cathode catalysts, and 33.48 mW/cm² and 52.08 mW/cm² when used as anode catalysts, respectively. The power density rises by 12% when the modified PtCo/C catalyst is employed as the anode catalyst and by 56% when it is used as the cathode catalyst, as compared to PtCo/C catalysts.

The ZrB₂-SiC ultra-high temperature ceramic is one of the most promising materials for the thermal protection system of hypersonic vehicles. However, the thermal protection system must meet the requirements of thermal protection capability and the lightweight characteristic at the same time. ZrB₂-20 vol.% SiC laminated ceramics with the same material compositions and different-sized particles for each sublayer were prepared by the spark plasma sintering method. Microstructures, grain size, elastic modulus, and hardness of the laminated ceramics were then characterized. Thermal insulation and thermal shock performance of laminated and monolithic ceramics were tested by a self-developed quartz lamp heating platform. The laminated ceramics were composed of three layers with large, medium, and small grain sizes, respectively. The elastic modulus and hardness of laminated ceramics gradually decrease layer by layer due to the different grain sizes. Compared with monolithic ceramics, the laminated ceramics have lower density and a similar cyclic thermal shock resistance, while the thermal insulation ability was obviously higher. The results proved that the ZrB₂–SiC laminated ceramics have a better application prospect in thermal protection systems.

In the current work, ytterbium oxide (Yb₂O₃) powders with the europium (Eu³⁺) were synthesized by the epoxide-driven sol–gel process. Yb₂O₃-europium xerogels were synthesized at different molar ratios (0, 2, 5, 8, 10, 20, 30, 40, and 50 mol%) and heat-treated at 1273 K in order to yield a dense crystalline material. The powders were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescent studies were performed to establish the relationship between their structural and luminescent properties. After a 1273 K heat treatment, the resultant powders consisted of spherical particles and presented different phases with well-defined reflections characteristic of a cubic-type crystalline structure, with crystallite sizes ranging from 14 to 30 nm. Finally, according to the luminescence studies, emission bands between 550 and 700 nm, due to the ⁵D₀ → ⁷F₂ transition level of the europium ion, were searched using wavelengths of 612 and 364 nm for excitation and emission, respectively.

The effects of adding Dy to the hydroxyapatite (HAp) structure were investigated experimentally and theoretically. The as-obtained experimental results with an increasing amount of Dy are as follows. X-ray diffraction, Raman, and Fourier transform infrared measurements verified the HAp structure for each specimen. The crystallinity, lattice parameters, lattice stress, strain, and anisotropic energy density were affected. Thermal stability and stoichiometry were not affected. It was observed that all the Dy-doped HAps have smaller crystallite size values compared to the un-doped HAp. The cell viability obtained from mouse fibroblast cell (L929) was higher than 82%, indicating all the samples were biocompatible. The theoretical findings, obtained from the density functional theory (DFT) calculations, exhibited a continuous decrease in the bandgap from 4.7109 to 3.7982 eV, an increase in the density from 3,155 to 3,189 kg m⁻³, and an increase in the linear absorption coefficient.

Various concentrations of europium-doped gadolinium oxide powders are synthesized by a high-temperature solid-state reaction method. Raman spectra of the compounds exhibited the vibrations and symmetry of monoclinic single-phase crystal formation, with the predominant monoclinic phase of Gd₂O₃ which is consistent with the XRD findings reported earlier. The core level electron emission spectra revealed the formation of highly valence-stable compound systems with shell structures corresponding to Eu³⁺ and Gd³⁺ electronic states. In-depth analysis of photoluminescence spectra with multiple emissions in the yellow–red region corresponding to transitions of ⁵D₀–⁷F₂, ⁵D₀–⁷F₁, and ⁵D₀–⁷F₀ which arise due to europium substitution brought out interesting findings of colourinescence parameters. Investigations of Judd–Ofelt parameters, mean lifetimes, radiative transition rates, and CIE coordinates revealed the compatibility of the prepared samples as the good orange-red emitter.

In the present study, the APS process was used to coat Al₂O₃, YSZ, and MSZ were applied on the surface of the IN738LC superalloy and NiCrAlY as the middle layer. The microstructure, porosity, and adhesion strength of these coatings were compared with the coating having the Al₂O₃ as the interlayer. Results showed that MSZ coating had less porosity compared to YSZ. Also, the presence of Al₂O₃ as an interface layer in the YSZ sample increased the porosity while in the MSZ sample the porosity decreased. With the presence of the Al₂O₃ layer, the size of the pores increased to the point that the largest porosity diameter in the Al₂O₃-MSZ sample was about 75 μm. Al₂O₃ showed highest adhesion strength (31 MPa) because of lower porosity. The high adhesion strength of Al₂O₃ can be attributed to diffusion and the formation of possible splats. The results showed that the Al₂O₃-MSZ sample had higher strength than Al₂O₃-MSZ with about 28 MPa. MgO seems to be a better and cheaper stabilizing additive than Y₂O₃.

This study investigates the effects of ZnO addition on the physicochemical and mechanical properties of zirconia-mullite composites. Zirconia-mullite composites containing varying amounts of ZnO (0–15 wt.%) were fabricated by sintering the mechanically activated gibbsite-zircon-kaolinite mixtures at 1550 °C. The results demonstrated the positive effect of adding up to 5 wt.% ZnO on optimizing the phase composition, surface characteristics, and mechanical properties of the fabricated composites. The stabilization of the tetragonal zirconia phase and the formation of the acicular mullite phase were positively affected by the presence of ZnO, as determined by X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses. The composites' flexural strength and diametral tensile strength (DTS) were increased from 65 to 155 MPa and 42 to 124 MPa, respectively, due to the stabilization of monoclinic zirconia and the formation of acicular mullite. Furthermore, a fracture toughness and Vickers microhardness of 4.67 ± 0.97 MPa.m^1/2 and 8 GPa were achieved in the composite containing 5 wt.% ZnO, respectively.

A new approach for the application of dye-synthesized solar cells is realized by using perovskite and single oxide micro/nanopowders. With respect to the literature, the desired energy efficiency of dye-synthesized solar cells is a priori established as perovskite and single oxide micro/nanopowders in a composite structure. In the present work, in order to produce dye-synthesized solar cells with FTO/TiO₂/ferroelectric/dye/electrolyte/Pt/FTO architecture, their precursor solutions were prepared by using nitrate-based salts, solvents, and chelating agents. The obtained gel films were dried at 200 °C for 2 h and then annealed at temperatures of 500 °C and 850 °C for 2 h in the air. TiO₂ and LaFeO₃ powders were characterized through DTA-TGA, FTIR, XRD, SEM, and UV-Vis spectrometer machines. In line with the results obtained, dye-sensitized solar cell production, which can also be called ferroelectric photovoltaic cells with a combination of TiO₂, was produced. It was found that the production of continuously applicable and sustainable dye-sensitive solar cells using LaFeO₃ with together TiO₂ powders can be useful as innovative and futuristic approaches.

In this study, ceramic foams were produced by adding porcelain polishing waste (PPW) at different proportions (0, 25, 50, and 75 wt.%) to natural zeolite. In addition, Na₂CO₃, as a foam stabilizer, was externally added to each one raw material mixture to provide a better micro pore structure. The compact parts shaped under 60 MPa load were sintered in an electrical furnace at 10 °C/min heating rate at 1150 °C for 2 h in an air atmosphere. The phase composition and pore morphology of the samples produced were examined using X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). The thermal properties from room temperature to 300 °C, flexural strengths before and after corrosion, and corrosion behaviors in dilute NaOH (10% by volume) solution at 100 °C of the produced ceramic foams were investigated. The increase in the PPW amount has caused an increase in the amount and dimension of pores. The total porosity and density of the light foams in four different compositions synthesized varied between 21.80–81.94% and 0.45–1.85 g/cm³, respectively. The flexural strength and thermal conductivity values at 25 °C of the samples were between 0.84–6.18 MPa and 0.21–0.80 W/m.K, respectively. The corrosion behaviors in NaOH aqueous solution at 100 °C of the ceramic foams produced were characterized in detail. It is determined that the weight loss increased with the increase in corrosion time and PPW amount in the samples. Ceramic foam production realized by adding porcelain polishing waste (PPW) to natural zeolite is a promising method for efficient recycling and reducing product cost.